Dense Wavelength Division Multiplexing (DWDM) is a technology that transmits multiple data signals using different wavelengths of light through a single optical fiber. Incoming optical signals are assigned to specific frequencies within a designated frequency band. The capacity of the optical fiber is increased when these signals are multiplexed out onto the fiber.
DWDM is protocol and bit rate independent so data signals using varying protocols such as asynchronous transfer mode (ATM), SONET, and internet protocol (IP) can be transmitted through the same data stream over a single optical fiber pair regardless of their speed and protocol differences. Each individual protocol remains intact during the transmission process because there is not an optic-electric-optic conversion during transmission with DWDM transmission. The fact that the signals are not terminated within the optical layer allows the independence of the bit-rates and protocols, thus allowing DWDM technology to be easily integrated with the existing equipment in the network.
Each incoming optical signal is assigned to a specific wavelength division multiplexer (WDM) optical wavelength (λ—lambda) laser. The λ is a unique color of light as identified in DWDM standards. The λ (along with other lambdas) passes through an optical multiplexer which allows the multiple lambdas (or wavelengths) to be transmitted over the same pair of fibers. At the other end, the customer end, the multiplexed signals are each filtered to a separate wavelength. The appropriate optical interface card is then used to reproduce the original client signal in an appropriate protocol from each wavelength.